Several factors generally are involved in maintaining clean and efficient gas turbine engines. Such factors may include both preventive and non-preventative maintenance that may involve unscheduled removals and installations. Periodic gaspath cleaning is a preventive maintenance practice that is recommended to minimize compressor and turbine contamination.
There are documented cases of one-time compressor wash improvements in TSFC (Total Specific Fuel Consumption) and EGT (Exhaust Gas Temperature) of 0.85% and 8° C., respectively; however, experience indicates that gaspath cleaning prior to contamination is beneficial. For example, one operator has reported a fleet TSFC improvement of 1.0% when performing engine gaspath cleanings every three months. Generally, the recommended gaspath cleaning interval is every 1000 to 1200 hours commencing after a heavy maintenance. Engine manufacturers have estimated a reduction of 1.0% TSFC and 10° C. EGT over a 6000 hour period with regular gaspath cleaning. Using this procedure, there may be no significant improvements noted after each wash since the interval selected was one which would ease contaminant removal rather than one which would result in a noticeable increase in TSFC and EGT prior to wash.
An additional benefit of gaspath cleaning washes is the reduction of turbine sulphidation. Engine manufacturers' tests have shown that gaspath cleaning washes remove water soluble substances applied to the turbine. For example, a large domestic operator using gaspath cleaning washes at 100 to 150 hour intervals with expanded repair limits has been successful in reducing turbine blade scrap rate due to sulphidation damage at 6200 hours from 100% to less than 5%. It should be noted that gaspath cleaning for sulphidation reduction generally requires much shorter time intervals between washes than those used for compressor cleaning.
There are different approaches to performing gaspath cleaning. Some operators use a hose to spray a cleaning solution into the intake side of the engine, while other operators use a J hook that is inserted from the tail pipe, through the bypass core, and positioned right in front of the 3rd stage compressor so that the stream is sprayed rearward. In addition, other operators use an adapter that goes from the igniter plug hole inside of the engine and spray the solution therein.
For example, U.S. Pat. No. 5,899,217, issued May 4, 1999 to Testman, provides an engine wash recovery system which uses a partial covering (Apron type) over a turbo propeller engine and not a turbojet or turbofan engine to prevent spillage of the cleaning liquid run through the engine at slow speed with a collector for the liquid. It includes a small drain hose from a low point in the engine and a larger hose from the engine exhaust duct. It does not completely enclose the engine and would not work with current turbojet or turbofan engines.
U.S. Pat. No. 2,804,903, issued Sep. 3, 1957 to Davies, shows a protective transparent cover for a jet engine for shipping the engine to protect the engine, prevent spillage of oils and fuels, allow the engine to be viewed, and provide sealable openings for a lift device to access the engine. This device has no means of interconnecting to a cleaning and filtering system.
U.S. Pat. No. 3,646,980, issued Mar. 7, 1972 to Peterson, claims a lightweight jet engine cowl cover to protect a jet engine from dust and contaminants while the jet is on the ground with an opening to allow workmen to enter the engine and the use of a translucent sheet to admit light.
Again, no provision is made for use during a gaspath cleaning maintenance operation.
U.S. Pat. No. 5,143,321, issued Sep. 1, 1992 to Jackson, describes a folding protective cover for turbo-engines to cover the air inlet and exhaust ducts while the plane is on the ground with handles and the use of lightweight material to assist in the installation and removal of the cover, which folds up into a compact size for carrying and storing. Again, no provision is made for use during a gaspath cleaning maintenance operation. A universally applied and completely enclosed system for covering and enclosing a turbojet or turbofan engine and interconnecting to a filtration system is needed.
Based on the foregoing, none of these approaches account for the waste produced from the cleaning operations of jet engines as described herein. The chemical cleaning spray and toxic particulates removed from gas turbine engines are hazardous waste and should not be dumped into a normal drainage system.
As such, there is a need for an affordable collection system and suit operable with various jet engine gaspath cleaning operations and that collect effluent and preventing spillage of the effluent from the cleaning operations. Thereby, the collection system and suit offer an economical and ecological solution for the cleaning of jet engines on a regular basis and the collecting, and potential filtering, of the toxic effluent so as to minimize the negative impact on the environment generally associated with gaspath cleaning.